Yazoo – Pleistocene Valley Train Braid Bar Woodland

Description

Removal of the historic natural communities of this site occurred long before thorough studies and investigations were conducted. Accordingly, reference conditions for this site have yet to be confirmed, but they are perceived to consist of mature forest stands that support a diverse mix of southern bottomland hardwoods adapted to the moderately well and well drained soils of this site. Once assigned or identified, the reference community will not represent the pre-settlement forest community, but it should identify an assemblage of naturally occurring species that reflects and contributes to regional biodiversity and local forest ecology. Implicated in the latter is that the “local” geomorphic features and drainage patterns of this soil-site environment should not have been drastically altered or removed (e.g., land leveled). Based on literature accounts, natural vegetation that may be most representative of this soil-site environment include components of Putnam’s (1951) “white oaks – red oaks – other hardwoods” forest type. This is corroborated by the species list for Dexter and Pearson soils in the Sunflower County, Mississippi soil survey manuscript (USDA-SCS, 1959).

The current state and transition model does not have a return or transition pathway from the altered states back to reference conditions. Former land uses (alternate states) that result in soil compaction (increased bulk densities), lower soil organic matter content, altered fertility, and smaller available rooting volume can reduce forest site productivity by 10 to 20 percent, if not more, for some species (Groninger et al., 1999) and may result in high seedling mortality. Attempts to establish reference conditions under these soil-site constraints could result in poor establishment and response, colonization by undesirable taxa, or failure. These soil-site impacts, however, can be ameliorated through various “afforestation” techniques such as plow pan breakup (subsoil or deep plowing), fertilization, and fallowing fields before stand establishment (Emile Gardiner, USFS Research Forester, personal communication). State 5 (Forest Recovery) is representative of forest establishment and growth on locations where soil compaction and reduction of nutrients have occurred. Once a previously affected location has recovered its site potential, transition to the reference state may be possible. Realistically, it may not always be possible to return to a “perceived” reference state from a former altered condition. While planting and establishing trees appropriate for a site may be possible, achieving restoration of the understory and other system functions present challenges that may never be realized (Stanturf et al., 2001; Flinn and Vellend, 2005). That potential transition is still under review and is currently not shown or addressed in the state and transition model.

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Description

This state is representative of the dominant land use activity on this ecological site, agriculture production. The dominant crops grown on this site are cotton (Gossypium hirsutum), corn (Zea mays), soybeans (Glycine max), and wheat (Triticum aestivum) (USDA-SCS, 1959; Snipes et al., 2005). Minor crops, such as some specialty crops (e.g., fruits, vegetables, and tree nuts such as pecans), may be grown locally.

The soils of this site are well suited to agriculture production. Tilth is reportedly good with a surface layer that is very friable and easily tilled and managed over a wide range of moisture content. Management concerns are largely centered on erosion, plow pan development, soil compaction under equipment traffic, crusting and packing following heavy rain, and low organic matter content (USDA-SCS, 1959; Snipes et al., 2005). Each of these factors could affect yields or impede optimum operation. Management measures to ameliorate some of these issues may include implementing a conservation tillage or management system and subsoiling to breakup plow pans (USDA-NRCS, 2006b). Major components that producers generally develop and plan are proper selection of crop cultivar, pest control, cropping system, tillage methods, nutrient management, and water management (Snipes et al., 2005). Key practices of some cropping systems often include two or more crops grown in a multiyear rotation, which has been documented to disrupt pest cycles. Leaving crop residue on the surface can help to maintain tilth, fertility, and organic matter content – all critical elements of soil quality and health. For monoculture cropping systems, the implementation of well-designed pest and nutrient management systems are imperative (Pringle et al., 2017). (For assistance, interested parties are advised to visit their local NRCS Field Office.)

Three separate management phases comprise this state: Conservation Management (2.1), Transitional Conservation Management (2.2), and Conventional Management (2.3). The three phases consist of varying tillage methods and approaches to soil health management systems.

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Description

This gently sloping ecological site typically adjoins nearly level to level landscapes. It is bordered by soils of varying textures and drainage characteristics. Accordingly, inconsistencies in wetness, ease of operation, and production or yields may occur across a cropped location. An increasingly common practice on this site consists of land forming or leveling surface irregularities into a predetermined and engineered, uniform slope. This practice removes the drier and higher features of this site, which are then used to fill wetter and lower positions (e.g., depressions or swales) across the targeted area. Advantages of land leveling may include reduced hazards of erosion and runoff rates, improved surface drainage, and enhanced distribution and conservation of irrigation water. Disadvantages of the practice is a churning of various surface and subsurface materials (former soil horizons) that no longer occur in a predictable or regular pattern. Organic matter content in the surface layer is generally low, and the surface tends to crust and pack after heavy rains (USDA-NRCS, 2006b). One potential hazard that appears to be emerging in some areas is an effective management of surface water runoff. As both irrigated and stormwater runs off leveled fields at uniform rates, surface water tends to collect cumulatively and simultaneously, which places tremendous demands on local drainage networks. Without “in field” structures (natural or artificial) to stagger runoff, the downslope (or lower) ends of some fields tend to back flood thereby contributing to more flooding overall in local watersheds (personal observations).

Immediately following land leveling, the constituent elements of soil health are likely to be absent. In some areas, producers have initiated practices such as applying organic residues (e.g., poultry litter) or growing rice crops for one to two years to rapidly boost fertility and introduce organic matter (via rice biomass) in the surface layer. Over time, the full complement of the management (or community) phases of State 2 may be possible on land leveled fields. They are not repeated or indicated here.

Currently, this state serves as an endpoint in the state and transition model because the ability to predict vegetation response when transitioning to a different state is no longer possible without soil-site investigations for each area of interest. The former soils of this ecological site, including surface and subsurface horizons, will have been redistributed as particles among other former soils.

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Description

This state is representative of areas that have been converted to and maintained in pasture or grassland. The soils of this site correspond to Pasture Suitability Group 8a for the State of Mississippi and are considered well suited to most commonly grown perennial forage species. Available water capacity is moderate to high, and production on this site is generally high when areas are adequately fertilized and properly managed. The very strongly to moderately acid reactions of these soils usually require lime for many forage species.

Given that this ecological site adjoins lower, wetter sites, some forage operations may utilize the higher elevations of this site as a protected area. This site may be suitable for the storage of harvested forage or holding of livestock when wet or flooded conditions occur on lower areas.

Establishing an effective pasture management program can help minimize degradation of the site and assist in maintaining growth of desired forage. An effective pasture management program includes selecting well-adapted grass and/or legume species that will grow and establish rapidly; maintaining proper soil pH and fertility levels; using controlled grazing practices; mowing at proper timing and stage of maturity; allowing new seedings to become well established before use; and renovating pastures when needed (Rhodes et al., 2005; Green et al., 2006).

This state consists of four community phases that represent a range of forage management options and pasture and hayland condition scenarios. Options range from establishing a forage monoculture for haying to a broad mixture of forage species for production and grazing. It is strongly advised that consultation with local NRCS Service Centers be sought when assistance is needed in developing management recommendations or prescribed grazing practices.

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Description

This state is representative of forest recovery in areas that were once under former intensive land use such as long-term row crop cultivation. Characteristics that distinguish this state from other forest states on this site include a suite of soil-site properties that reportedly affect tree growth such as higher soil bulk density due to compaction, presence of a plow pan, lower organic matter content, and reduced fertility (Baker and Broadfoot, 1979; Groninger et al., 1999). Two community phases are provisionally recognized for this state. Community Phase 5.1 represents natural colonization of tree and shrub species without management. Community Phase 5.2 is representative of intentional forest establishment by artificial regeneration or planting.

For Community Phase 5.2, determining the objectives and goals of the future stand is imperative to increase the probability of successful establishment and production of the afforested area. These decisions will ultimately determine the species to be established, preparation requirements, planting density, and post-planting operations (e.g., competitor control, future improvement cuttings and thinnings, regeneration methods, and overall stand health). Since each area targeted for afforestation may have unique or different land use histories, having a clear understanding of the soil-site conditions are essential. Some areas may necessitate a series of soil improvement actions prior to planting. These actions may include subsoiling or deep plowing to breakup plow pans and fertilizing the targeted area. An additional option is to allow the area to undergo fallowing for a predetermined period (Community Phase 5.1) to potentially increase soil organic matter content, enhance soil aggregate stability, increase soil biological activity, and improve water holding capacity and infiltration rates. Controlling competing vegetation (chemical and mechanical treatment) will most likely be critical. Post-planting operations and maintenance of the stand can enhance survival, future development, and achieve goals and objectives (see Gardiner et al., 2002).

Finding the appropriate approach for a given environment necessitates close consultation with trained, experienced, and knowledgeable forestry professionals. If there is a desire to proceed with this state, it is strongly urged and advised that professional guidance be obtained and a well-designed afforestation and silvicultural plan developed in advance of any work conducted. For an exceptional review and summarization of the afforestation literature, techniques, and practices within the Southern Mississippi River Alluvium, interested parties are directed to Gardiner et al. (2002).

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Description

This state is representative of the range of conservation actions that may be implemented and established on this ecological site. Apart from planting trees and managing for forest, one may elect to establish native herbaceous species and manage for predominantly a native grassland; a complex mixture of native grasses and forbs; or a pollinator planting whereby native forbs dominate the mix. In each of these options, it is strongly advised (possibly a programmatic requirement) that the species comprising the planting or seed mix consist of spring, summer, and fall flowering species. Depending on goals and objectives, various conservation programs and practices may be available. For additional information and assistance, please contact or visit the local NRCS Field Office.

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